The present invention relates to a driving method and apparatus for a light source element such as a laser diode, which is included in an optical pickup that performs data read/write operations for an optical disc.
Generally, optical discs have a helical track. Using a light source element such as a laser diode, recorded data is read out from or recorded in the track. The optical pickup provided with the light source element should correctly trace the track during the reading or recording of data. This is called tracking, and a tracking error signal is generated for tracking control. If a tracking error occurs during a data reading mode, the wrong data is read out. If a tracking error occurs during a writing mode, the data is recorded at the wrong position.
If the wrong data is read out, that data is abandoned, and the tracking operation is again performed for reading out the desired data. However, in the case of a writing mode, the data may be recorded at a position where other data has already been recorded, thereby losing data.
FIG. 1 is a block diagram illustrating a conventional driving apparatus for a light source element. The conventional apparatus includes a mode selector 101, a reference power data generator 102 and a drive signal generator 103.
In FIG. 1, mode selector 101 is for selecting the driving mode of an optical pickup and generates a mode signal M based on user manipulation. For example, the mode signal M may be a logic "low" when the driving mode is set for reading data and may be a logic "high" when the driving mode is set for writing data. Reference power data generator 102 generates reference power data PREF in accordance with mode signal M. Generally, a light source element requires less power for read operations than for writing. Besides varying in accordance with the driving mode, the power required for driving the light source element also varies according to the kind of optical disc used for reading/writing the data. Therefore, the reference power data suitable for a given optical disc should be recorded in the disc's lead-in area. Accordingly, based on the data read out from the optical disc, reference power data generator 102 generates reference power data which, in accordance with mode signal M, is either for a reading mode or for a writing mode. In other words, reference power data generator 102 generates a read reference power data for reading and a write reference power data for writing. The reference power data PREF is applied to drive signal generator 103 where it is converted into a driving signal DR and then applied to a light source element such as a laser diode installed in the optical pickup.
As described above, in the conventional driving apparatus of a light source element, the light source element is operated at a constant power irrespective of pickup position. Thus, even if the optical pickup is disposed in an incorrect position due to poor tracking, which may result from incorrect operation of the driving apparatus, an external impulse signal, minor impacts, disc imperfections, dust on the disc, etc., the light source element maintains a constant power level. Therefore, if a tracking error occurs during writing, the previously recorded data is lost by overwriting additional data.